Jim's Random Notes

I’m in the process of (re)organizing my garage to remove clutter and turn it into a woodworking shop of sorts. Not that it’ll be what you call a well-stocked shop, even for a hobbyist. My power tool collection includes two bandsaws (see below), a compound miter saw, some drills, a circular saw, jigsaw, and belt sander. Maybe a few other hand tools. Still, one can build a surprising number of things with those few tools.

But the garage currently has a few major problems. Most importantly it’s cluttered with 15+ years of stuff, much of which I have no use for. That has to go, and I need to organize what’s left. The workbench, too, needs to be replaced. Ever since we’ve been in this place, the workbench’s primary use has been as a place to hold stuff that I don’t have a place for. That is, there’s stuff piled on it. And it’s not really designed for wood working. It’s too tall, a little too long for the space it’s in, and too deep.

I’ve been looking at shop layouts to get ideas of how I want to organize my garage work area. I have a few restrictions, though, that make things a bit more difficult.

First, the garage is primarily for storing cars. With the Mustang gone, we now have two cars and two garage bays, and I rather like the idea of parking my truck in the garage. Whatever I do, I have to ensure that I can still pull my truck into the garage.

There is an 8 foot wide area beside one of the bays (where the workbench is), so it’s possible to have both cars in the garage and still have space for other things. My idea is to organize the space so that I can store everything in that 8′ space. When I need to work on a project, I can pull the truck out and spread out the tools. So pretty much everything has to be on wheels.

My first step in that direction will be adding a mobile base to my bandsaw. Perhaps to two different bandsaws, since I recently acquired a second one. My original machine, purchased used two years ago, is a Craftsman 12″ bandsaw, built in 1987 or so. It has a 3/4 horsepower motor and with a 1/2 inch blade has no trouble cutting through a 6″ mesquite log. My only real complaints with the machine are that it’s difficult to move, and changing blades is a bit of a pain in the neck. If I want to cut up a log and then cut out some patterns I have to install the 1/2 inch blade, rough-saw the log, and then install the smaller blade (1/4 or 3/16 inch) for the detail cuts.

A friend of mine recently cleaned out his garage and gave me his old bandsaw that he hasn’t used in years. It, too, is a Craftsman 12″ bandsaw, although it’s 10 years older and only has a 1/2 inch motor. But fitted with a 3/16 inch blade it should be perfect for cutting stuff up to about 4 inches thick. Having two bandsaws should prevent me from having to change blades except when they need to be replaced.

Although my primary concern is wood carving, I’m also interested in trying my hand at building some simple furniture, some storage shelves, and other things. Before I get additional tools, I need an appropriate workbench that I can use for projects. I also need additional storage space. So I’m looking at plans for a rolling workbench with built-in storage. I don’t know yet whether that storage will be shelves or drawers. But once I build that, I can free up some of the space that’s currently being occupied by my big workbench.

Wood storage is a problem. I put a couple of 4′ x 8′ pieces of cheap plywood above the rafters, giving me a lot of space in which to store lumber, and perhaps there’s enough space up there to store my carving wood, too, if I organize things better.

The next task will be storage. Currently, we have a mish-mash of shelving units scattered throughout the garage. It works, but it’s less than ideal. I can make better use of the wall space if I build custom shelves.

On the strictly carving front, I’ve had a bad run of mistakes lately. Over the weekend I cut out blanks for three shallow spoons and two of those stirrers with holes in them. I broke one of the stirrers (cut it too thin and it snapped while I was working with it) and one of the spoons. I carved the bowl on one of the other spoons too deeply and went through the bottom. The third spoon will likely survive, although I carved it a bit too deeply, too. It’s very thin on the bottom. I found a quicker way to hollow out the spoon bowls, but in doing so got a bit too aggressive.

It’s nice having the bandsaw working again, though. I cut out a couple of animal caricatures over the weekend that should turn out to be fun to carve. We’ll see.

I’m hoping to get the garage organized in the next four or five weeks so that I can enjoy working (playing) in there when it cools off. In the summer (especially this summer), it gets unbearably hot in there before noon. But the weather in October and November and even the first part of December should be great for working in the garage.

Eventually I’ll have a dedicated workshop that has air conditioning and heating. Even then, space will be somewhat limited. So the work I’m doing now to put the tools, workbench, and other things on wheels will be quite useful in the future.

The Janka hardness test measures the resistance of a type of wood to withstand denting and wear. It measures the force required to embed a 11.28 mm (0.444 inches) diameter steel ball into wood to half the ball’s diameter. Why 11.28 mm? Because a circle with a diameter of 11.28 mm has an area of 100 square millimeters.

Of course, wood hardness depends on if you’re talking about side hardness (imagine pressing against the side of a tree) or end hardness (imagine pressing into the top of a stump that you cut off). It also depends on the wood’s moisture content and a few other factors. The numbers you’ll see most often are for side hardness at 12% moisture content.

The important thing to know about the Janka scale is not so much the absolute number (which can be given in pounds-force, kilograms-force, newtons, or kilonewtons), but rather the relative difference between two species. For example, mesquite with a hardness rating of 2,345 lbf is quite a bit harder than purpleheart (1,860 lbf).

When I first started carving, I was told that the Janka rating gives a good idea of the difficulty of cutting a particular type of wood. Seeing that mesquite is harder than purpleheart, I thought that I could carve some great things from purpleheart. How wrong I was! Whereas mesquite cuts very nicely, purpleheart is very difficult to cut. It’s so hard that it damaged my knife blade.

Most oaks have a Janka hardness rating around 1,350 but, as with purpleheart, I find them more difficult to cut than mesquite. Obviously, the Janka scale doesn’t tell the whole story.

I’ve done quite a bit of searching and haven’t found anything similar to the Janka scale that gives the relative cutting resistance of different woods. Many woodworking sites will give informal measurements. For example, mesquite is said to have “low cutting resistance” and purpleheart has “moderate cutting resistance.” In those cases, it’s the resistance to cutting with a saw rather than with a knife, but it does give me a little more evidence to back up my statement that the Janka scale is not the thing to use in determining cutting resistance.

In his 1950 Ph.D. thesis, Cutting force in wood working (just the abstract is free; I haven’t been able to find a free copy of the thesis), Eero Kivimaa did a lot of research to determine the forces involved in cutting wood. He did most of his research using air-dried Finnish birch, but some tests with 21 different wood species led him to write in his Summary:

The cutting force was found to vary approximately linearly with the specific gravity of wood (air-dry Finnish Birch). The cutting force rose to a maximum when the moisture content increased up to 10-13 %, and fell again with higher moisture content. Comparison of results obtained with 21 species showed that it is possible to estimate the main cutting force of any wood species on the basis of its sp. gr.

Aha! If you look up the specific gravity of mesquite, you’ll find that it’s about 0.80. The specific gravity of purpleheart is 0.86. From Kivimaa’s research, then, you would expect purpleheart harder to cut. Southern live oak, which is pretty common around here, has a specific gravity of 0.88. Again, these woods are “softer” than mesquite on the Janka scale, but have higher specific gravity and are more difficult to carve. Hickory, too, has a lower Janka rating (1,820), but a specific gravity of 0.83.

Note that, as with Janka hardness, the force required to cut a particular type of wood will depend a lot on the moisture content. As Kivimaa pointed out, force required increased as moisture content increased to between 10 and 13 percent, and then decreased as moisture content increased. “Green” wood will cut more easily than kiln dried wood.

Cutting force required will also depend on the sharpness of the knife, the bevel angle, the angle of attack, whether you’re carving with the grain, across the grain, or on the end grain, the smoothness of the blade as is moves through the wood, and the type of cut (pressing or slicing). We can hold those values constant in order to get a relative cutting resistance measure.

I’m not convinced that specific gravity is the sole deciding factor, but it’s much better than Janka hardness in determining how hard a wood will be to cut.

A good place to find information about a particular type of wood, including its hardness and specific gravity, is The Wood Database.

Speaking of specific gravity, common wisdom is that wood floats. Whereas it’s true that most woods float, there are some species that sink. Lignum vitae, Arizona desert ironwood, some types of Ebony, and many other species have specific gravity greater than 1.0. Even kiln dried, these woods are more dense than water, meaning that they will not float in water. Black ironwood has a specific gravity of 1.49; it’s 50% more dense than water.

I finally finished my Whittle Pup tutorial. If you’re interested in how I carve my little dogs or if you want to give it a try yourself, check it out.

Carving the Whittle Pup

When working with a power carver (think, Dremel), you have to be very careful about protecting yourself from the effects of wood dust. Dust collection is a big deal to power carvers. And even when hand-sanding a small carving, one has to be careful. The effects of inhaling wood dust are uncomfortable at best and at worst, deadly.

This is especially true when carving “found wood.” If you’re working with basswood, the effects of inhaling a few dust particles will be a slight cough and maybe a sore throat for a few days. You probably don’t want to inhale a lot of it, though. But unless you inhaled enough basswood dust to physically block your lungs, you wouldn’t die from it.

Not all woods are as benign as basswood.

Large pieces (3 inches or more thick) of poison ivy, for example, have beautiful grain. But you don’t see people carving the stuff because most people are highly allergic to it. Other woods that cause allergic reactions on contact include (among many others) poison oak, poison sumac, walnut, and fig. Most people are allergic to the poison oak, ivy, and sumac. Allergies to walnut and fig are not uncommon, but usually not as severe. In any case, serious health problems due to contact allergies are rare.

That’s not so with dust. The dust from many different types of wood can cause severe respiratory problems. Pages such as this Toxic Wood Chart list dozens of species whose dust can be the cause of everything from mild skin irritation to severe respiratory distress. Wood dust can be deadly toxic.

A common ornamental tree here in Texas is called “mimosa.” It’s a medium-sized tree, fast growing, with beautiful flowers that have a very pleasant odor. The trees typically live 20 to 30 years. There’s been a lot of development in my area in the last 30 years, and I’m seeing more dead mimosa trees. The heartwood is beautiful. I want to carve the stuff, but somebody told me, “mimosa is deadly toxic.” I don’t take much on faith these days, so I thought I’d do some research to see if it really is toxic.

There are many dozens of plants that are commonly called “mimosa.” So far as I can tell, the only thing those plants have in common is that they are members of the family Fabaceae, or the legume family. The sub-family Mimosoideae contains many of the plants called “mimosa.” But the tree we commonly call mimosa around here is probably Albizia julibrissin, which is not very closely related to Mimoseae. To further confuse matters, several species of Acacia are also referred to as “mimosa.” Those, too, have some nice looking wood that I’m sure people carve.

I can undoubtedly discover the exact type of tree we’re calling “mimosa” around here, but I don’t know how to determine whether or not it’s toxic. I suppose I could try working it without wearing any kind of mask or filter, but that seems like a high-risk endeavor. I’d rather somebody could tell me one way or the other.

Mind you, I typically wear a simple mask when sanding or working with the power carver, but if this stuff is as toxic as the charts say then I’ll want to wear something a bit more protective and that includes a full face mask. I don’t have any qualms about carving the stuff, but if I’m going to raise dust then I need to be a lot more careful.

There’s a disconnect between botanists and wood carvers. Botanical sites tell me lots of things about the trees, including what parts of the tree are toxic when ingested. But botanical sites don’t tell me if the dust is toxic. And wood carving sites will tell me that “mimosa” is toxic, but they don’t tell me which type of mimosa they’re referring to!

This isn’t uncommon, by the way. There are over 600 different species referred to as “oak,” and “willow” covers around 400 species. “Cypress” encompasses dozens of different species, most in the same genus but not all. And don’t even get me started on ironwood, which can mean any one of a couple dozen species.

In any case, I’d sure like it if botanical sites included information on dust toxicity, and if wood carving sites were more specific in identifying their woods.

I should mention here that if you’re working with a wood that you can’t identify, or if you can identify the type of wood but don’t know where it came from, you should be cautious. Pallets, for example, often contain useful wood. The wood might be easily identified, but pallets are often treated with some rather nasty chemicals that, if inhaled, can cause some serious problems. Old doors or tables that were finished with some type of stain or varnish can also be dangerous. The same thing goes with fungi that cause spalting in maple and in other woods. Some of those fungi, if inhaled, will want to set up shop in the warm, dark, moist environment in your lungs. Fungus can be a problem even in kiln-dried wood such as the ambrosia maple that I love working with.

When in doubt, wear a protective mask.

I’ve spent most of my limited carving time recently on more spoons. A few of the little bears, but that’s about it.

My friend Mike was about to throw an old table into the burn pile up at the ranch. I grabbed a few slats to bring home, because I wanted to see what kind of wood was hiding under all that rot.

The wood turned out to be teak. I now have the entire table and will be making things from it.

I got ambitious on Sunday and made another mesquite log spoon. This one turned out really nice.

Finally, another coffee scoop. The wood used is ambrosia maple. I’m getting better with the square or rectangular bowls.